A functional element of this kind is shown in FIG. 6 of the PCT application with the publication number WO 01/03880 and indeed as a variant of a bolt element, the head part and shaft part of which have at least substantially the same diameter. The corresponding PCT application led amongst other things to the European patent 1 202 834. A bolt element of this kind is sold by the company Profil Verbindungstechnik GmbH & Co. KG in the form of a so-called spherical bolt which is claimed per se in the European patent 1 346 160. The bolt element is riveted to a sheet metal part such as the tail gate of a vehicle in the area of the head part, with the end of the shaft part remote from the head part being provided with a spherical shape. The spherical end of the shaft part then forms a part of a ball joint, the socket of which is part of a gas spring which serves to support the tail gate.
A similar functional element is for example known from the German patent specification 34 47 006 and is realized there is a threaded bolt, with the head part being provided with a tubular piercing and riveting section which is adapted to pierce a sheet metal part and for the subsequent formation of a rivet bead, whereby the element is secured in the sheet metal part. Between the tubular piercing and riveting section the head part has a flange with a ring surface standing perpendicular to the longitudinal axis of the element and the ring surface is normally arranged after the introduction of the element into a sheet metal part just below the side of the sheet metal part adjacent the shaft part.
The piercing slug formed on piercing the sheet metal part is pressed into the piercing and riveting section and thereby assists the rivet connection with the sheet metal part. DE-PS 34 47 006 however also describes functional elements in the form of nut elements, where the shaft part can be understood to be an extension of the head part and this is provided with an internal thread. The shaft part does not however have to be designed as a thread, many designs can be considered, for example a guide spigot or pin-like design on which for example carpets can be secured by means of corresponding clips.
Such functional elements, i.e. in accordance with DE-PS 34 47 006 C2 have proven themselves over many years and make it possible to produce a high-quality connection between the element and the sheet metal part. However such elements are relative expensive to manufacture and require in part the use of extremely precisely operating cold heading machines which operate relatively slowly to achieve the desired quality. The need to use relatively expensive cold heading machines and the restricted working speed leads to relatively high production costs. Moreover, for some applications, it will be more favorable if the weight of the elements could be reduced.
In a functional element in accordance with FIG. 6 of WO 01/03880 it is problematic that the element requires a considerable deformation of the head part on the attachment to a sheet metal part and becomes deformed in undesired manner, whereby the quality of the connection suffers. A disadvantage of this kind is not acceptable in mass production where thousands of functional elements are used and indeed not even if the undesired deformation only occurs occasionally, because such events disturb the production sequence quite apart from the undesired scrap.